Field of the Invention
The present invention relates to a multi-component graft copolymer and a thermoplastic resin composition thereof which has excellent physical properties especially high weather durability and impact strength. More particularly, it relates to a multi-component graft copolymer and a polymethyl methacrylate composition thereof or a polyvinyl chloride composition thereof which has excellent impact strength and weather durability.
It is known that a brittle hard resin can be blended to a natural or synthetic rubber or that a monomer for hard resin can be graft-polymerized on an elastic polymer to prepare a transparent resin composition having high impact strength.
It is also known that the graft copolymer produced by a graft polymerization of the monomer on the elastic polymer or the composition of the graft copolymer and a hard resin have superior physical properties to those of the mixture of the elastic polymer and the hard resin because of superior mutual solubility of the elastic polymer and the base resin.
Usually, methyl methacrylate resin or a composition comprising a main component of methyl methacrylate has superior transparency, luster and weather durability to those of the other resins, and has excellent physical properties and shape-stability at high temperature. However, the resin has not enough impact strength and is brittle and the improvement of these properties has been desired.
It has been well-known that vinyl chloride resins have excellent physical and chemical properties and have been widely used in various fields. However, disadvantageously vinyl chloride resins have not enough impact strength. Various studies for improving the property has been conducted.
It has been known to improve the impact strength by blending a hard resin such as a polymethyl methacrylate or a polyvinyl chloride to MBS resin which is produced by a graft-polymerization of styrene and methyl methacrylate on a polybutadiene elastic polymer or ABS resin which is produced by a graft-polymerization of styrene and acrylonitrile on a polybutadiene elastic polymer.
However, the compositions of the hard resin and the MBS resin or ABS resin have inferior weather durability whereby the compositions could not be used outdoors. At the initial stage after the molding, the compositions have enough high impact strength. However, when the compositions are used outdoor, the high impact strength of the composition could not be maintained. The impact strength is rapidly lowered. The main reason of the lowering of the impact strength has been considered to be based on the deterioration of polybutadiene in the MBS resin or the ABS resin by ultraviolet rays.
It has been studied to use an elastic component other than polybutadiene having weather durability as the impact strength improver from the above-mentioned viewpoint.
Typical resins include a graft copolymer produced by a graft-polymerization of a monomer for hard resin on an elastic copolymer of ethylene and vinyl acetate or a graft copolymer produced by a graft-polymerization of a monomer of styrene, methyl methacrylate or acrylonitrile on an elastic core polymer of polyalkyl acrylate.
However, these impact strength improver could not impart enough impact strength increasing effect in comparison with those of the compositions of the hard resin and the MBS resin or the ABS resin. The physical properties of the hard resin such as tensile strength and heat deformation temperature may be sometimes remarkably lowered by the blend to certain graft copolymer.
The inventors have studied to improve the hard resin with a graft copolymer having an elastic core component of polyalkyl acrylate which has excellent weather durability.